Sewage Treatment Plants (STP) make use of chemical and biological processes to remove contaminants (suspended solids) from sewage and wastewater. Sewage treatment plants efficiently treat the wastewater to produce reusable recycled water. The recycled water generated through STPs is safe to be discharged back to the environment. Along with good quality recycled water, good quality compost generation also becomes a possibility with STPs.
Stages of treatment in a STP
There are four stages of treatment in a Sewage Treatment Plant
- Preliminary treatment: – Removes bigger articles like of plastic bottles, rags, wrappers, soiled diapers and pads, coarse objects and materials.
- Primary treatment: – The sludge, involving the organic and inorganic solids, settle to the bottom of the sedimentation tank, leaving the lighter solids, grease and oil to the surface using skimmers. This removes at least 60% of solids, allowing the wastewater to seep into the next stage of treatment.
- Secondary treatment: – This stage involves separation of biological floc from the liquid through aerobic biological processes. Indigenous microorganisms consume biodegradable soluble contaminants, to intensively clean water (up to 90%).
- Tertiary treatment: – The remainder water is treated to a stage where pathogens, nitrogen, phosphorus and other inorganic compounds are reduced substantially. Here, the water is treated chemically, through ultraviolet light or micro filtration before finally releasing into the environment. Meanwhile, the sludge is subjected to further treatment. It goes into digester tanks with anerobic bacteria, before becoming ready as compost.
Sewage treatment guidelines and norms by the Indian government:
Sewage treatment norms have undergone massive change since 2015. In 2019, more stringent norms around STP have come into place. For instance, in metro cities like Mumbai, housing projects with more than 20,000 sq meters are given clearance only if they treat solid waste in-house. This has forced several gated communities to set up a functional and a compliant STP structure in place. 2019 also witnessed a stronger guideline regarding treated effluent. According to the new laws, all new and old STP’s will need to follow the following revised standards
- BOD (Biochemical Oxygen Demand) level – 10mg/L
- pH value – 5.5-9.0
- Total Suspended Solids – 10mg/L
- Nitrogen – 10mg/L
- COD (Chemical Oxygen Demand) – 50
- Fecal Coliform – 230 per 100 milliliters
Modern, eco-friendly Sewage Treatment Plants
- Are not energy intensive and hence more economical.
- Uses Anaerobic Microbial Inoculum (AMI), to treat organic waste.
- Are easy to install and operate.
- Becoming an environmentally responsible individual is easy with the right kind of Sewage Treatment Plant. Evaluate your sustainability goals and choose a Sewage Treatment Plant that works in your favor.